An intervention to be reviewed: the importance of the microclimatic study of the detached wall paintings in the Loggia della Casa dei Cavalieri di Rodi in Rome

This contribution deals with the study of the causes of deterioration of the late 15th century wall paintings in the Loggia della Casa dei Cavalieri di Rodi in Rome, detached from the wall support during the 1979 restoration. The painted area of approximately 183 square metres located in situ on artificial sandwich supports made of fibreglass and polyurethane foam is now deteriorated. In order to understand the causes of the deterioration of the decorative painting cycle, it was necessary to conduct a microclimatic and climatic study of the environment. It emerged that the paintings are subject to strong daily thermo-hygrometric stress and thermal peaks linked to direct sunlight. These factors have caused irreversible processes. Extensive areas of lacunae and micro lacunae in the paint film can be observed, which are explained by the thermal and photochemical factors linked to sunlight. The alternation of thermo-hygrometric cycles results in stresses of a physical nature, with contractions and expansions occurring both on the surface and between the preparatory layers and the artificial support, resulting in adhesion defects. The artificial substrate is also affected by daily thermal fluctuations and tends to move, generating stresses at the anchoring points. Over time, the deficiency of the anchorage from the back of the substrates generated deformations within the same panel, which flexes, resulting in cracks and falls of the original mortar. As far as turbulence is concerned, while on the one hand it allows for aeration and the abatement of condensation phenomena during the winter season, on the other hand it creates an erosion problem due to the solid particles it carries. In addition, climatic weather factors represent a further aggravation for the conservation of the pictorial cycle as the surface is in direct contact with changes in the external climate. In view of the above, it is now necessary to rethink the conservation of the Loggia with a multi-disciplinary approach that takes into account the peculiar microclimate.